Does it have to be a PDF? You can open the first PDF in PS to flatten the text and save as JPEG for lower file size. I do this all the time to email proofs.
If you still want it to be a PDF, you can place the flattened JPEG file back into InD (hide all other layers) and save as PDF again. Just be sure to Crop To: Trim Box if you have bleeds. Should be smaller file size. Good luck!